With an increase in communication demand, the number of network devices that are connected to one network is increased, and a network configuration is complicated. For example, because each router within the network individually controls a route over which a packet is transferred, a packet route is difficult to flexibly configure over the network as a whole.
In contrast, in a network to which a software defined network technology (SDN) is applied, because a function of controlling each network devices is integrated into one piece of software, it is possible to flexibly configure a route. For example, in an open flow network (OFN), a function of controlling a packet route is separated from a relay device for the packet, and is integrated into a single network management server. It is possible for the network management server to flexibly configure the packet route over the whole network by setting the routing information indicating the transmission source of the packet to each relay device.
The network management server can set the routing information to a server equipped with various functions as well as the relay device within the network. The routing information, for example, is generated based on a destination address or a source address within a header of the packet.
For example, with regard to transfer of the packet, Japanese Laid-open Patent Publication No. 2001-352337 discloses that when the packet is relayed over different domains, the source address or the destination address of the packet is changed.